std::is_lvalue_reference

// is_lvalue_reference example
#include <iostream>
#include <type_traits>

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_lvalue_reference:" << std::endl;
  std::cout << "int: " << std::is_lvalue_reference<int>::value << std::endl;
  std::cout << "int&: " << std::is_lvalue_reference<int&>::value << std::endl;
  std::cout << "int&&: " << std::is_lvalue_reference<int&&>::value << std::endl;
  return 0;
}